1. Field of the invention
The present invention relates to document feeding mechanisms, and more particularly to a low level indicator for such feeding mechanisms. In applications requiring the feeding of particular documents, such as envelopes and the like, especially in high-speed environments, it is inconvenient to require operator intervention when the paper supply is depleted. The time required to replenish the depleted paper supply is time lost from the main processing line to which the documents are directed. Avoidance of the shut down of a feeder mechanism for reloading during a run is therefore desirable.
Particularly in multiple-feeder operations, it is desirable to provide an indication of low paper whenever it occurs during a run so that a large scale processing line employing a plurality of supplied documents may be continually replenished prior to actual shut down of any one feeder which in turn would necessitate shut down of the entire run.
2. Description of the Prior Art
The patent to Lillibridge, 4,585,221, provides an optical sensor for an envelope stack but operates to turn the machine off when the stack diminishes to a preset level, rather than indicating that an operator should refill the stack to maintain operation.
The patent to Saito, 3,971,918, discloses optical measurement of the number of a plurality of stacked corrugated cardboards, to provide an indication of the count, but does not indicate a manner wherein signals can be provided to the operator to refill the stack to maintain operation prior to shut down of the machine.
The patent to Nakata, 4,467,949, shows a paper detector for controlling a paper feed device, but does not provide a system wherein early warning signals may be provided to an operator prior to depletion of paper supply during a high-speed run.
Particularly in multiple-feeder operations, it is desirable to provide an indication of low paper whenever it occurs during a run so that a large scale processing line employing a plurality of supplied documents may be continually replenished prior to actual shut down of any one feeder which in turn would necessitate shut down of the entire run.